Wideband Reception and Processing for Dual-Polarization Radars with Dual Transmitters

Abstract

Oversampling pulsed Doppler radar returns at a rate larger than the pulse bandwidth, whitening the range samples, and subsequent averaging has been pursued as a potential way to decrease the measured standard deviation of signal parameter estimates. It has been shown that the application of oversampling, whitening, and subsequent averaging improves the quality of reflectivity, mean velocity, and spectral width estimates in agreement with theory. Application of this procedure to a dual-polarization radar with dual transmitters is evaluated in this paper. Oversampled data collected from the Colorado State University (CSU)-University of Chicago-Illinois State Water Survey (CHILL) radar using a wideband receiver are analyzed to evaluate the performance of dual-polarization parameter estimators, such as differential reflectivity and differential phase. The negative impact of relative phase characteristics of the transmitted pulses in two polarizations on the copolar correlation, and subsequently on polarimetric parameter estimation, is analyzed. CSU-CHILL radar's transmitted pulse sampling capability is used to evaluate the impact of the transmitted waveform's mismatch on whitening and estimation.

Processing of Oversampled Signals in Range on Polarimetric Weather Radars with Mismatched Channels

“…The pattern for these mismatches is based on Choudhury and Chandrasekar's (2007) work on the CSU-CHILL radar and on our observations from the National Severe Storms Laboratory Next Generation Weather Radar (NEXRAD) polarimetric prototype (Ivi c et al 2003b). An amplitude mismatch could be due to miscalibrated pulse-forming networks or different overall gains in each channel.…”

“…Rangeoversampling techniques rely on the precise knowledge of the range correlation of oversampled signals, which is a function of the transmitter pulse envelope, the receiver filter impulse response, and the distribution of scatterers illuminated by the radar. In contrast, recent experimental results on a dual-transmitter system have revealed some difficulties: if the amplitude and/or phase mismatch between transmission pulses is disregarded in the formulation of the decorrelation transformation, processing of range-oversampled dual-polarization signals with the standard whitening transformation can produce abnormally biased 1 polarimetric variable estimates (Choudhury and Chandrasekar 2007). In contrast, recent experimental results on a dual-transmitter system have revealed some difficulties: if the amplitude and/or phase mismatch between transmission pulses is disregarded in the formulation of the decorrelation transformation, processing of range-oversampled dual-polarization signals with the standard whitening transformation can produce abnormally biased 1 polarimetric variable estimates (Choudhury and Chandrasekar 2007).…”

Oversampling and Whitening with the CASA Radar

“…It has been shown in [8] that a phase mismatch between transmitted waveforms leads to the degradation of the cross-correlation estimated from whitened data. The magnetron transmitter used in the MA-1 radar does not have the ability to control the phase of the transmitted waveform unlike the klystron transmitters, and phase correction methods have been applied to the data to compensate for this.…”

Adaptive Range Oversampling to Achieve Faster Scanning on the National Weather Radar Testbed Phased-Array Radar

“…Range oversampling provides more samples for the estimation of meteorological variables; these samples can be transformed (decorrelated) and efficiently used to reduce the variance of estimates and/or reduce the required observation times (dwell times). Theoretical and simulation studies demonstrating the advantages of these techniques (Torres and Zrnić 2003a,b) have been successfully verified on weather data collected with experimental setups and offline signal processing (Ivić et al 2003b;Torres and Ivić 2005;Choudhury and Chandrasekar 2007;Hefner and Chandrasekar 2008). However, a real-time implementation of range oversampling processing on weather radars has not been reported to date.…”